It is not necessary to unistall Windows Defender; just ensure it is not running in real time.
Click Start, on 'Search programs and files' type 'Windows Defender.'
On the Windows Defender page click 'Tools' then 'Options' and make sure than 'Real Time Protection' is unchecked.
It won't do any harm to install Windows Defender updates and do the ocassional scan but make sure that real time protection is kept off otherwise it will clash with BullGuard real time protection.
Also make sure that the Windows Firewall is not enabled.
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